Update object and Insert relational objects

 My question is pretty simple.  However, I was unable to get my development done with the examples provided in the help file.

1. I have a UI that calls a retrieve method. ( Find<> ).  I get a strongly typed object ( Model1).  I update some values of this object , example Model1.Description = " Updated Description";

2. To save this object, my UI calls my Business Objects project and sends this updated Model1 as a parameter.  My Business Object, does the following

Calls the same retrieve method ( Find <> ), Gets an object Model2 and sets its value of Model1 ...   Model 2 = Model 1.

3. Then I do a SaveChanges();

Instead of updating existing object, it creates a new object and adds it to the database.

So, how do I update an existing object ?

Also, if my object has dependency ( Lets say I have a Foreign Key on other table ), how do I update records for this kind of relationship.

Here is how I did that:

Given is a saved "Project" with association to a "Customer" and a Project may have several SubProjects:

      // Edit
      RootProject projectToEdit;
      using (EntitiesUnitOfWork uow = CreateUnitOfWork())
      {
        projectToEdit = (from
                           p in uow.RootProjects
                         where
                           p.Name.Contains("Test")
                         select
                           p
                         )
                         .SingleOrDefault();

        // Quick and dirty: force loading of the associated Customer
        // and SubProjects within the UnitOfWork (normaly done via the Aggregate extension
        // Method).
        string dummy = projectToEdit.Customer.Name;
        int dummyCount = projectToEdit.SubProjects.Count;

      }

      projectToEdit.Name = "Testing";
      projectToEdit.Customer.Name = "Wilma Feuerstein";
      projectToEdit.SubProjects.Add(new SubProject
                                      {
                                        Backlog = new Backlog(),
                                        Name = "Another Subject ",
                                        Description = "Description",
                                        Status = new ProjectStatus(true, false),
                                        Customer = projectToEdit.Customer
                                      });
     
      using (EntitiesUnitOfWork uow = CreateUnitOfWork())
      {
        uow.Attach(projectToEdit);    // *** read below
        uow.SaveChanges();
      }

***
With the "Attach" method you reassign the loaded Entity to a UnitOfWork. The "SaveChanges()" saves all changes (inserts, updates) within the object graph. Attach a logger to the Context and watch what SQL gets submitted to the Database.

Sörnt

To update an existing object, modify its properties and call SaveChanges on the unit of work:

using (IUnitOfWork uow = context.CreateUnitOfWork())
{
  Product p = uow.Find<Product>(...)[0];
  p.Description = "Yummy goodness";
  uow.SaveChanges();
}

To update an association, just set the association property or the relevant foreign key property, i.e. either of the following:

p.Manufacturer = uow.FindById<Manufacturer>(123);  // setting the association
p.ManufacturerId = 123;  // setting the FK property

Again this will be committed only when you call SaveChanges.